"""
Shared EES (Explore Education Statistics) API client.

Two APIs are available:
  - Statistics API: https://api.education.gov.uk/statistics/v1  (only ~13 publications)
  - Content API:    https://content.explore-education-statistics.service.gov.uk/api
    Covers all publications; use this for admissions and other data not in the stats API.
    Download all files for a release as a ZIP from /api/releases/{id}/files.
"""
import io
import zipfile
from pathlib import Path
from typing import Optional

import requests

STATS_API_BASE = "https://api.education.gov.uk/statistics/v1"
CONTENT_API_BASE = "https://content.explore-education-statistics.service.gov.uk/api"
TIMEOUT = 60


def get_publication_files(publication_slug: str) -> list[dict]:
    """Return list of data-set file descriptors for a publication (statistics API)."""
    url = f"{STATS_API_BASE}/publications/{publication_slug}/data-set-files"
    resp = requests.get(url, timeout=TIMEOUT)
    resp.raise_for_status()
    return resp.json().get("results", [])


def get_latest_csv_url(publication_slug: str, keyword: str = "") -> Optional[str]:
    """
    Find the most recent CSV download URL for a publication (statistics API).
    Optionally filter by a keyword in the file name.
    """
    files = get_publication_files(publication_slug)
    for entry in files:
        name = entry.get("name", "").lower()
        if keyword and keyword.lower() not in name:
            continue
        csv_url = entry.get("csvDownloadUrl") or entry.get("file", {}).get("url")
        if csv_url:
            return csv_url
    return None


def get_content_release_id(publication_slug: str) -> str:
    """Return the latest release ID for a publication via the content API."""
    url = f"{CONTENT_API_BASE}/publications/{publication_slug}/releases/latest"
    resp = requests.get(url, timeout=TIMEOUT)
    resp.raise_for_status()
    return resp.json()["id"]


def download_release_zip_csv(
    publication_slug: str,
    dest_path: Path,
    zip_member_keyword: str = "",
) -> Path:
    """
    Download the full-release ZIP from the EES content API and extract one CSV.

    If zip_member_keyword is given, the first member whose path contains that
    keyword (case-insensitive) is extracted; otherwise the first .csv found is used.
    Returns dest_path (the extracted CSV file).
    """
    if dest_path.exists():
        print(f"    EES: {dest_path.name} already exists, skipping.")
        return dest_path

    release_id = get_content_release_id(publication_slug)
    zip_url = f"{CONTENT_API_BASE}/releases/{release_id}/files"
    print(f"    EES: downloading release ZIP for '{publication_slug}' ...")
    resp = requests.get(zip_url, timeout=300, stream=True)
    resp.raise_for_status()

    data = b"".join(resp.iter_content(chunk_size=65536))
    with zipfile.ZipFile(io.BytesIO(data)) as z:
        members = z.namelist()
        target = None
        kw = zip_member_keyword.lower()
        for m in members:
            if m.endswith(".csv") and (not kw or kw in m.lower()):
                target = m
                break
        if not target:
            raise ValueError(
                f"No CSV matching '{zip_member_keyword}' in ZIP. Members: {members}"
            )
        print(f"    EES: extracting '{target}' ...")
        dest_path.parent.mkdir(parents=True, exist_ok=True)
        with z.open(target) as src, open(dest_path, "wb") as dst:
            dst.write(src.read())

    print(f"    EES: saved {dest_path} ({dest_path.stat().st_size // 1024} KB)")
    return dest_path


def download_csv(url: str, dest_path: Path) -> Path:
    """Download a CSV from EES to dest_path."""
    if dest_path.exists():
        print(f"    EES: {dest_path.name} already exists, skipping.")
        return dest_path
    print(f"    EES: downloading {url} ...")
    resp = requests.get(url, timeout=300, stream=True)
    resp.raise_for_status()
    dest_path.parent.mkdir(parents=True, exist_ok=True)
    with open(dest_path, "wb") as f:
        for chunk in resp.iter_content(chunk_size=65536):
            f.write(chunk)
    print(f"    EES: saved {dest_path} ({dest_path.stat().st_size // 1024} KB)")
    return dest_path